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Weed trimmer heads contain trimmer line on a spool and a bump knob on the bottom to extend more line. Depressing the throttle trigger on a weed trimmer powers the trimmer head to turn through a cable in the trimmer shaft. Trimmers require a replacement head when the threads strip due to use of heavier line than recommended or heavy usage. Replacing a trimmer head is similar on gasoline and electric trimmers.

Turn your weed trimmer off and allow it to cool completely. Disconnect the power cord from an electric model or disconnect the spark plug boot from a gas model.

Wipe off the trimmer head with a shop towel to remove grass clippings and debris.

Remove the bump knob on the bottom of the trimmer head. Depending on your make and model of trimmer, it will turn counterclockwise, have tabs to press in and pull it straight off, or remove by pressing in the tabs and turning it.

Pull the trimmer line spool out of the trimmer head.

Observe your trimmer head to see if it has a small hole in the inner and outer portions. If so, insert a small Phillips screwdriver into the two holes to hold it in position, remove the center nut with an adjustable wrench and pull the head off.

Pry the trimmer head off a trimmer without holes in the head with a flathead screwdriver to loosen it. Pull the old trimmer head off the nut on the bottom of the shaft.

Insert a replacement head on the trimmer shaft. Block the holes with a small Phillips screwdriver and replace the center nut with an adjustable wrench on models that have an exterior nut.

Insert the two loose ends of the trimmer line spool through the eyes on the exterior of the trimmer head. Refasten the bottom bump knob onto the head.

Replace the spark plug boot on a gasoline trimmer.

Things You Will Need

Shop towel

Small Phillips screwdriver

Adjustable wrench

Flathead screwdriver

Warning

Do not use a cut or fraying extension cord on an electric weed trimmer.

Unplug extension cords on electric trimmers by pulling the plug only, and not the cord.

About the Author

Mary Lougee has been writing for over 10 years. She holds a Bachelor's Degree with a major in Management and a double minor in accounting and computer science. She loves writing about careers for busy families as well as family oriented planning, meals and activities for all ages.